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Biomedical subjects

D V Gokhale

Publications and source records attributed to D V Gokhale.

8 recordsLinked to original sources
PubMed1995

Industrial yeast strain improvement: construction of a highly flocculent yeast with a killer character by protoplast fusion.

Conditions were optimized for rapid release and improved regeneration of protoplasts of Saccharomyces cerevisiae NCIM 3458. Rapid protoplast release was also obtained with representatives of several other yeast genera under the modified conditions of treatment. The application of the procedure in construction of a highly flocculent Saccharomyces cerevisiae with a killer character is described. Fusion was effected between UV-killed protoplasts of S. cerevisiae NCIM 3578 with a killer character and live protoplasts of the highly flocculent S. cerevisiae NCIM 3528 in the presence of polyethylene glycol (PEG) 6000. Fusants were selected using benomyl resistance as marker, the killer toxin producer rather than the highly flocculent yeast being resistant to the fungicide at a concentration of 100 micrograms ml-1. Fusants were also characterized by their DNA contents, capacity for ethanolic fermentation of molasses sugar and levels of invertase, alcohol dehydrogenase and pyruvate decarboxylase activities.

Cloning, Molecular↗
PubMed1992

Protection of Aspergillus niger cellulases by urea during growth on glucose or glycerol supplemented media.

The cellulase enzymes of Aspergillus niger were found to undergo catabolite repression in the presence of glucose and glycerol accompanied by sudden drop in pH of the fermentation medium below 2.0. This sudden drop in pH caused inactivation of cellulolytic enzymes produced by Aspergillus niger. The supplementation of nitrogen sources, especially urea, protects A. niger cellulases from inactivation caused by a sudden drop in pH, since urea helped to maintain the pH of the fermentation medium between 3.5 and 4.5. The role of urea in the protection of cellulase was more prominent when it was used in combination with glycerol (5%).

Aspergillus niger↗
PubMed1991

Optimization of cellulase production by Aspergillus niger NCIM 1207.

Aspergillus niger NCIM 1207 produces high levels of extracellular beta-glucosidase and xylanase activities in submerged fermentation. Among the nitrogen sources, ammonium sulfate, ammonium dihydrogen orthophosphate, and corn-steep liquor were the best for the production of cellulolytic enzymes by A. niger. The optimum pH and temperature for cellulase production were 3.0-5.5 and 28 degrees C, respectively. The cellulase complex of this strain was found to undergo catabolite repression in the presence of high concentrations of glucose. Glycerol at all concentrations caused catabolite repression of cellulase production. The addition of glucose (up to 1% concentration) enhanced the production of cellulolytic enzymes, but a higher concentration of glucose effected the pronounced repression of enzymes. Generally the growth on glucose- or glycerol-containing medium was accompanied by a sudden drop in the pH of the fermentation medium to 2.0.

Aspergillus niger↗
PubMed1990

Association of logistic and Poisson models of infection with some physical characteristics of a single component plant virus.

A logistic model was recently formulated to describe the relationship between concentration of a single component plant virus and infections produced by inoculation to a local lesion host. In this paper the logistic is combined with a Poisson model. The logistic makes accurate fitting possible for a variety of infection-dilution series; and the Poisson acts as a base line, indicating whether lesion numbers are compatible with the hypothesis that random infection of similar infection sites has occurred. A logarithmic form of the logistic equation gives a straight line with negative slope (logit slope) which is useful in characterizing dilution series to which the logistic is fitted. A modified Poisson equation can also be fitted to a range of dilution series; it provides an independent estimate of slope for curves not widely divergent from the standard Poisson. Models have also been developed to define the limits of concentration within which single virions are likely to be randomly dispersed in inoculum without immediate contact with other virions, and are therefore more likely to enter inoculated tissue independently and cause random infections. Models are formulated for aggregation of tobacco mosaic virus in monolayers, crystals, and lenticular aggregates. Published and unpublished data are fitted and analyzed using some of these models.

Models, Statistical↗
PubMed1988

Confirmation and certainty in toxicology screening.

Confirmation of presumptive positive urine drug screens, necessary to minimize the reporting of false-positive results, can be costly and time-consuming. The predictive value model can be used to select the confirming tests and to calculate the confidence of the result. The predictive value of a test result is the probability, based on the sensitivity and specificity of the test, that the result is a true positive or a true negative. The predictive value model applied to toxicology screening tests for drugs of abuse showed that prevalence, in addition to sensitivity and specificity, was the factor controlling the confidence level of a result. For example, the predictive value of a positive result for a screening test that has a sensitivity of 99% and a specificity of 99%, applied to screening in a population with a prevalence of 1% is 0.50; for a prevalence of 10%, it is 0.92. Confirmation with a second, chemically independent, test of equal sensitivity and specificity increases the predictive value to 0.99.

Algorithms↗
PubMed1987

Relationship between plant virus concentration and infectivity: a 'growth curve' model.

A logistic ('growth curve') model is formulated and applied to the relationship between numbers of infections (local lesions) produced by a virus on inoculated plants and the concentration of the virus in the inoculum. This model has the advantages of being simple, data-based and therefore not founded on limiting postulates, and of being applicable to a wide range of infection-dilution series, including those obtained from multicomponent viruses. Here, it is applied to common tobacco mosaic virus. Examples of infection-dilution series taken from the literature are fitted more closely and more objectively than they were fitted by the original authors. A limiting number for lesions is estimated by minimizing chi 2 values for differences between observed lesion numbers and those calculated from the logistic equation. The complete fitting procedure can be programmed on a hand-held calculator.

Models, Biological↗
PubMed1979

The statistical treatment of correlated bilateral traits in the analysis of cranial material.

At present there is no standardized method to derive frequencies from bilateral non-metric traits. In this paper the commonly used methods are evaluated in light of statistical considerations and degree of sample preservation. In particular, we explore the question of dependence between sides for the bilateral traits. Several workers have tested for bilateral trait correlation in incorrect ways, confusing tests for differences in side frequencies with tests for independence. An easy method to test for independence, using the chi-squared test, is recommended. This test is used on 16 bilateral traits in a large sample of prehistoric carnia from Central California and significant dependence is found for all 16 of these traits. We suggest the traditional method of deriving frequencies be used. Both sides of the cranium should be considered, dividing the number of times the trait occurs by the number of sides available for observation. This method can be used even in poorly preserved samples. Side to side correlation may be compensated for by modifying the constants subtracted in the mean measure of divergence and in the expression for the approximate variance of the mean measure of divergence when the samples are drawn from identical populations.

California↗